**1.1 Energy overview in Africa**

Energy plays a central role in national development process as a domestic necessity and major factor of production, whose cost directly affects price of other goods and services (Amigun and von Blottnitz, 2008). It affects all aspects of development, such as social, economic, political and environmental, including access to health, water, agricultural productivity, industrial productivity, education and other vital services that improve the quality of life. Currently, many African countries experience frequent blackouts and the cost of electricity blackouts is not known. The continent's energy consumption and demand is expected to continue to grow as development progresses at rates faster than those of developed countries. The desire for improved quality of life and rises in population together with energy demands from the transport, industrial and domestic sectors will continue to drive this growth. Ensuring the provision of adequate, affordable, efficient and reliable high-quality energy services with minimum adverse effect on the environment in sustainable way is not only pivotal for development, but crucial for African countries most of which are struggling to meet present energy demands (Amigun et al., 2008). African countries need sustainable energy supplies to be in a position to improve their overall net productivity and become major players in global technological and economic progress. Unreliable energy supply may account for the low levels of private investment the African continent attracts and the poor economic productivity of its limited industries. Improvement

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Anaerobic Biogas Generation for Rural Area Energy Provision in Africa 37

Africa is a net energy exporter, but the majority of its population lacks access to modern fuels, and many countries rely on imported energy. More than 500 million people living in sub-Saharan Africa do not have electricity in their homes and rely on solid forms of biomass (firewood, agricultural residues, animal wastes, etc) to meet basic energy needs for cooking, heating and lighting. The disadvantages of these traditional fuels are many: they are inefficient energy carriers and their heat is difficult to control, they produce dangerous emissions and their current rate of extraction is not sustainable. The unsustainable use of fuel wood biomass can accelerate deforestation and lead to soil erosion, desertification and increased risk of flooding and biodiversity loss. The low levels of modern (commercial) energy consumption prevalent in Africa besides the heavy usage of traditional (noncommercial) biofuels- primarily biomass is also due to largely underdeveloped energy resources, poorly developed commercial energy infrastructure, widespread and severe poverty which makes it impossible for people to pay for conventional energy resources and the landlocked status of some African countries that make the cost of importing commercial energy more expensive (World Bank, 2003; Amigun et al., 2008). The existing aging and neglected facilities for thermal and hydro energy production need rehabilitation and expansion for the efficient delivery of useful energy services. Upgrading the abundant biomass in Africa to higher-quality energy carriers could help change the energy situation in the continent. The problems arising from non-sustainable use of fossil fuels and traditional biomass fuels have led to increased awareness and widespread research on the accessibility of new and renewable energy resources, such as biogas. The development of renewable energy technologies and in particular biogas technology can help reduce the dependence on non-renewable resources and minimise the social impacts and environmental degradation

problems associated with fossil fuel (Amigun and von Blottnitz, 2008).

This is illustrated in Figure 1.

supplementing other existing energy sources.

**1.2 The role of renewable energy: Biogas technology (anaerobic digestion)** 

As mentioned above, the economic prosperity and quality of life of a country are closely linked to the level of its per capita energy consumption and the strategy adopted to use energy as a fundamental tool to achieve the same (Amigun et al. 2008; Singh & Sooch 2004).

Renewable energy could provide the much desired sustainable rural revitalization in most developing countries. It is an ideal alternative because it could be a less expensive option for low income communities. An ideal renewable energy source is one which is locally available, affordable and can be easily used and managed by local communities. Anaerobic digestion is one of a number of technologies that offers the technical possibility of decentralized approaches to the provision of modern energy services using resources such as; cow dung, human waste and agricultural residues to produce energy. Anaerobic digestion of the large quantities of municipal, industrial and agricultural solid waste in Africa can provide biogas that can be used for heat and electricity production and the digester residue can be recycled to agriculture as a secondary fertilizer. Anaerobic digestion systems are relatively simple, economical, and can operate from small to large scales in urban and rural locations (Amigun & von Blottnitz, 2009). In this regard, many African governments have realised that renewable energies could play a very important role in

in the quality and magnitude of energy services in developing countries is required for them to meet developmental objectives including the Millennium Development Goals (MDGs). Africa is not only the poorest continent in the world but it was the only major developing region with negative growth in income per capita during 1980-2000 (World Bank, 2003).

Although reliable regional energy statistics are not readily available, existing estimates of energy use in Eastern and Southern Africa indicate a significant and persistent dependence on traditional biomass energy technologies and limited use of modern, sustainable energy technologies (Karekezi, 1994a). Biomass in the form of mainly wood-fuel and charcoal is the dominant energy source used in sub-Saharan Africa

Because of the shortage in commercial modern energy and current economic situation in most African countries, the fuel substitution away from biomass is less likely because of declining disposable incomes for both urban and rural population. There is fuel-switch back to traditional fuels as modern fuels become scarce in some areas but the wood fuels are also becoming scarce in some countries. Biomass is cheap but when used in an unplanned (unsustainable) manner leads to consumption beyond regenerative limits with serious environmental consequences. On average, about 40% of total commercial energy is consumed in six countries in the Northern sub-region and a similar share in Southern Africa with over 80% by South Africa. The other 45 or more countries share the remaining 20%. Similarly, the major oil and gas producers are limited to about ten countries in the North and West regions while about 95% coal (anthracite in nature) is produced in South Africa. This uneven distribution of the fossil energy resources (crude oil and natural gas) on the African continent is reflected in the energy production and consumption patterns (Table 1). As a result, 70% of countries on the continent depend on imported energy resources, which support the need to harness the available abundant renewable energy resources (Amigun, 2008).


aMajor energy exports are in excess of 0.5 quads

bMost of the African countries energy imports are very small (less than 0.3 quads)

Table 1. The energy distribution in Africa indicating countries which export and import energy (Amigun et al., 2008)

in the quality and magnitude of energy services in developing countries is required for them to meet developmental objectives including the Millennium Development Goals (MDGs). Africa is not only the poorest continent in the world but it was the only major developing region with negative growth in income per capita during 1980-2000 (World Bank, 2003).

Although reliable regional energy statistics are not readily available, existing estimates of energy use in Eastern and Southern Africa indicate a significant and persistent dependence on traditional biomass energy technologies and limited use of modern, sustainable energy technologies (Karekezi, 1994a). Biomass in the form of mainly wood-fuel and charcoal is the

Because of the shortage in commercial modern energy and current economic situation in most African countries, the fuel substitution away from biomass is less likely because of declining disposable incomes for both urban and rural population. There is fuel-switch back to traditional fuels as modern fuels become scarce in some areas but the wood fuels are also becoming scarce in some countries. Biomass is cheap but when used in an unplanned (unsustainable) manner leads to consumption beyond regenerative limits with serious environmental consequences. On average, about 40% of total commercial energy is consumed in six countries in the Northern sub-region and a similar share in Southern Africa with over 80% by South Africa. The other 45 or more countries share the remaining 20%. Similarly, the major oil and gas producers are limited to about ten countries in the North and West regions while about 95% coal (anthracite in nature) is produced in South Africa. This uneven distribution of the fossil energy resources (crude oil and natural gas) on the African continent is reflected in the energy production and consumption patterns (Table 1). As a result, 70% of countries on the continent depend on imported energy resources, which support the need to harness the available abundant renewable energy resources (Amigun,

Major energy exportera Net energy exporter Importersb Nigeria Angola Benin Algeria Cameroon Eritrea Libya Congo Ethiopia

Ghana

Congo

Egypt Cote d' Ivoire Kenya Gabon Gabon Morocco Congo Sudan Mozambique Namibia Senegal Tanzania Togo Zambia Zimbabwe

bMost of the African countries energy imports are very small (less than 0.3 quads)

Table 1. The energy distribution in Africa indicating countries which export and import

South Africa Democratic Republic of

aMajor energy exports are in excess of 0.5 quads

energy (Amigun et al., 2008)

dominant energy source used in sub-Saharan Africa

2008).

Africa is a net energy exporter, but the majority of its population lacks access to modern fuels, and many countries rely on imported energy. More than 500 million people living in sub-Saharan Africa do not have electricity in their homes and rely on solid forms of biomass (firewood, agricultural residues, animal wastes, etc) to meet basic energy needs for cooking, heating and lighting. The disadvantages of these traditional fuels are many: they are inefficient energy carriers and their heat is difficult to control, they produce dangerous emissions and their current rate of extraction is not sustainable. The unsustainable use of fuel wood biomass can accelerate deforestation and lead to soil erosion, desertification and increased risk of flooding and biodiversity loss. The low levels of modern (commercial) energy consumption prevalent in Africa besides the heavy usage of traditional (noncommercial) biofuels- primarily biomass is also due to largely underdeveloped energy resources, poorly developed commercial energy infrastructure, widespread and severe poverty which makes it impossible for people to pay for conventional energy resources and the landlocked status of some African countries that make the cost of importing commercial energy more expensive (World Bank, 2003; Amigun et al., 2008). The existing aging and neglected facilities for thermal and hydro energy production need rehabilitation and expansion for the efficient delivery of useful energy services. Upgrading the abundant biomass in Africa to higher-quality energy carriers could help change the energy situation in the continent. The problems arising from non-sustainable use of fossil fuels and traditional biomass fuels have led to increased awareness and widespread research on the accessibility of new and renewable energy resources, such as biogas. The development of renewable energy technologies and in particular biogas technology can help reduce the dependence on non-renewable resources and minimise the social impacts and environmental degradation problems associated with fossil fuel (Amigun and von Blottnitz, 2008).

### **1.2 The role of renewable energy: Biogas technology (anaerobic digestion)**

As mentioned above, the economic prosperity and quality of life of a country are closely linked to the level of its per capita energy consumption and the strategy adopted to use energy as a fundamental tool to achieve the same (Amigun et al. 2008; Singh & Sooch 2004). This is illustrated in Figure 1.

Renewable energy could provide the much desired sustainable rural revitalization in most developing countries. It is an ideal alternative because it could be a less expensive option for low income communities. An ideal renewable energy source is one which is locally available, affordable and can be easily used and managed by local communities. Anaerobic digestion is one of a number of technologies that offers the technical possibility of decentralized approaches to the provision of modern energy services using resources such as; cow dung, human waste and agricultural residues to produce energy. Anaerobic digestion of the large quantities of municipal, industrial and agricultural solid waste in Africa can provide biogas that can be used for heat and electricity production and the digester residue can be recycled to agriculture as a secondary fertilizer. Anaerobic digestion systems are relatively simple, economical, and can operate from small to large scales in urban and rural locations (Amigun & von Blottnitz, 2009). In this regard, many African governments have realised that renewable energies could play a very important role in supplementing other existing energy sources.

Anaerobic Biogas Generation for Rural Area Energy Provision in Africa 39

The anaerobic digestion process will occur at most temperatures below 70°C, but in the commercial operation of digesters two main temperature ranges are typically employed; the mesophilic range (30-44°C ) and thermophilic range (45-60°C). In addition to sewage sludge, organic farm wastes, municipal solid waste, green botanical waste and organic industrial waste have also been used as feedstock in various small to large scale digesters across the world. Current commercial anaerobic digestion processes generally involve the following steps; pre-treatment (including size reduction and the separation of non-biodegradable substances), digestion, biogas cleaning and conditioning (to remove CO2, water vapour and other undesirables), and subsequently biogas utilization (via internal combustion engines, or the more efficient combined heat and power plant (CHP)). The solid residue from the

Various types of small to medium scale biogas digesters have been developed including the floating drum, fixed dome, and plastic bag design (Amigun & Blottnitz 2007). The amount of biogas produced from a specific digester depends on factors such as the amount of material fed, the type of material, the carbon/nitrogen ratio, and digestion time and temperature (Omer & Fadalla 2003; Schwart et al. 2005; Chynoweth et al. 2001). Depending on the context, any type may be used. However, most of the small to medium scale biogas plants built so far are of the fixed dome type (Amigun & von Blottnitz 2009). The technology is gradually gaining popularity in developing countries, especially in Africa where the lack of clean and sustainable energy source represents damage to the environment and its people (Amigun & von Blottnitz 2009). In addition, Sub-Saharan Africa with its warm climates is

In the subsequent sections of this chapter, the current state of status of biogas technology in sub-Saharan Africa will be presented, along with a discussion of opportunities and challenges faced. The socio-economic benefits of biogas digesters is also been investigated through the use of case studies of commercial and demonstration plants on the continent. The economics of biogas technology in terms of investment and maintenance in the rural

Biogas technology is viewed as one of the renewable technologies in Africa that can help eases its energy and environmental problems. To date, some digesters have been installed in several sub-Saharan countries, utilising a variety of waste such as from slaughterhouses, municipal wastes, industrial waste, animal dung and human excreta. Small-scale biogas plants are located all over the continent but very few of them are operational. In most African countries, for example, Burundi, Ivory Coast, and Tanzania, biogas is produced through anaerobic digestion of human and animal excreta using the Chinese fixed-dome digester and the Indian floating-cover biogas digester, which are not reliable and have poor performance in most cases (Omer and Fadalla, 2003). These plants were built for schools, health clinics and mission hospitals and small-scale farmers, in most cases by nongovernmental organisations. In Africa the interest in biogas technology has been further stimulated by the promotional efforts of various international organisations and foreign aid agencies through their publications, meetings and visits. Most of the plants have only operated for a short period due to poor technical quality. Table 3 gives a list of the African countries with biogas production units as at 2007. There is thus a need to introduce more

digestion process (called digestate) can be used as compost.

well-suited for the biogas digester technology (Aboyade 2004).

**2. Biogas technology overview and status in Africa** 

African context is discussed.

Fig. 1. Human development index (HDI) and per capita electricity consumption, 2003 –

Anaerobic digestion describes the natural breakdown of organic matter in the absence of oxygen into a methane rich gas (biogas) via the complex and synergistic interactions of various micro-organisms types including hydrolytic, fermentative, acidogenic, and methanogenic bacteria (Lusk et al. 1996, Parawira, 2004b). The first group of microorganism secretes enzymes, which hydrolyses polymeric materials such as proteins and polysaccharides to monomers such as glucose and amino acids. The fermentative bacteria convert these monomers to organic acids, primarily propionic and acetic acid. The acidogenic bacteria convert these acids to hydrogen, carbon dioxide, and acetate, which the methanogens utilize via two major pathways to produce methane and carbon dioxide (Lusk et al. 1996; Verma 2002). The potential for organic matter decomposition to generate a flammable gas has been recognized for more than 400 years. In 1808, it was determined that methane was present in the gases produced during the anaerobic digestion of cattle manure. In 1868, Bechamp, a student of Pasteur attempted to isolate the microorganism responsible for the anaerobic bioconversion of ethanol to methane.

The first practical application of anaerobic digestion for energy production took place in England in 1896 when biogas from sewage sludge digestion was used to fuel street lamps. As is the case for many other renewable technologies, interests in anaerobic digestion suffered with the rise of the dependence of petroleum. However some developing countries, mainly in Asia, embraced the technology for the small scale provision of energy and sanitation services (Monnet 2003). Since that time, anaerobic digestion has received considerable interest to harness its waste disposal and energy producing capabilities, with municipal sewage disposal attracting the widest application (Lusk et al. 1996).

2004, (Source: UNDP, 2006)

Fig. 1. Human development index (HDI) and per capita electricity consumption, 2003 –

Anaerobic digestion describes the natural breakdown of organic matter in the absence of oxygen into a methane rich gas (biogas) via the complex and synergistic interactions of various micro-organisms types including hydrolytic, fermentative, acidogenic, and methanogenic bacteria (Lusk et al. 1996, Parawira, 2004b). The first group of microorganism secretes enzymes, which hydrolyses polymeric materials such as proteins and polysaccharides to monomers such as glucose and amino acids. The fermentative bacteria convert these monomers to organic acids, primarily propionic and acetic acid. The acidogenic bacteria convert these acids to hydrogen, carbon dioxide, and acetate, which the methanogens utilize via two major pathways to produce methane and carbon dioxide (Lusk et al. 1996; Verma 2002). The potential for organic matter decomposition to generate a flammable gas has been recognized for more than 400 years. In 1808, it was determined that methane was present in the gases produced during the anaerobic digestion of cattle manure. In 1868, Bechamp, a student of Pasteur attempted to isolate the microorganism responsible

The first practical application of anaerobic digestion for energy production took place in England in 1896 when biogas from sewage sludge digestion was used to fuel street lamps. As is the case for many other renewable technologies, interests in anaerobic digestion suffered with the rise of the dependence of petroleum. However some developing countries, mainly in Asia, embraced the technology for the small scale provision of energy and sanitation services (Monnet 2003). Since that time, anaerobic digestion has received considerable interest to harness its waste disposal and energy producing capabilities, with

municipal sewage disposal attracting the widest application (Lusk et al. 1996).

**Nigeria** 

**Nigeria** 

2004, (Source: UNDP, 2006)

for the anaerobic bioconversion of ethanol to methane.

The anaerobic digestion process will occur at most temperatures below 70°C, but in the commercial operation of digesters two main temperature ranges are typically employed; the mesophilic range (30-44°C ) and thermophilic range (45-60°C). In addition to sewage sludge, organic farm wastes, municipal solid waste, green botanical waste and organic industrial waste have also been used as feedstock in various small to large scale digesters across the world. Current commercial anaerobic digestion processes generally involve the following steps; pre-treatment (including size reduction and the separation of non-biodegradable substances), digestion, biogas cleaning and conditioning (to remove CO2, water vapour and other undesirables), and subsequently biogas utilization (via internal combustion engines, or the more efficient combined heat and power plant (CHP)). The solid residue from the digestion process (called digestate) can be used as compost.

Various types of small to medium scale biogas digesters have been developed including the floating drum, fixed dome, and plastic bag design (Amigun & Blottnitz 2007). The amount of biogas produced from a specific digester depends on factors such as the amount of material fed, the type of material, the carbon/nitrogen ratio, and digestion time and temperature (Omer & Fadalla 2003; Schwart et al. 2005; Chynoweth et al. 2001). Depending on the context, any type may be used. However, most of the small to medium scale biogas plants built so far are of the fixed dome type (Amigun & von Blottnitz 2009). The technology is gradually gaining popularity in developing countries, especially in Africa where the lack of clean and sustainable energy source represents damage to the environment and its people (Amigun & von Blottnitz 2009). In addition, Sub-Saharan Africa with its warm climates is well-suited for the biogas digester technology (Aboyade 2004).

In the subsequent sections of this chapter, the current state of status of biogas technology in sub-Saharan Africa will be presented, along with a discussion of opportunities and challenges faced. The socio-economic benefits of biogas digesters is also been investigated through the use of case studies of commercial and demonstration plants on the continent. The economics of biogas technology in terms of investment and maintenance in the rural African context is discussed.
